“The food may be triggering inflammation in the gut mucosa [the innermost layer of the gastrointestinal tract and a major part of the body’s immune system],” says one of the study's authors, Tanuja Chitnis, MD, a professor of neurology and the medical director of the Comprehensive Longitudinal Investigation of Multiple Sclerosis at the Brigham and Women's Hospital (CLIMB) study at Partners Multiple Sclerosis Center in Boston. “Our study suggests that inflammation brought about by food allergies may be important in causing or enhancing disease activity.”

Dr. Chitnis and her colleagues add that food allergies may also change the gut bacteria, creating neuroactive chemicals that affect the central nervous system.

Self-Reported Allergy Questionnaire Plus MRI Reveal Trends

The study included 1,349 individuals with MS (344 men and 1,005 women) who had enrolled in the CLIMB program and had an average disease duration of 16 years. Researchers totaled the number of MS attacks each person had had over the course of their illness. Participants completed a self-reported questionnaire on their allergies. A total of 753 had an MRI scan with gadolinium, performed within about 90 days of a clinic visit when the allergy questionnaire was completed.

MRIs enhanced with the contrast agent gadolinium highlight areas of inflammation (active lesions) in the brain. According to the National Multiple Sclerosis Society, normally, a cell layer surrounding blood vessels in the brain and spinal cord keeps substances from passing from the bloodstream into the central nervous system. Gadolinium highlights inflamed areas where this blood-brain barrier has broken down.

Of all those participating in the study, 427 had no known allergy and 922 had one or more allergies, with 586 reporting an environmental allergy, 238 a food allergy, and 574 an allergy to prescribed drugs.

The food allergies reported were allergies to eggs, dairy, wheat, soy, fish, shellfish, fruits, nuts, and other food products. Among environmental allergies were those to pollen, grass, trees, dust mites, and pets.

More Relapses and Active Lesions in the Food Allergy Group

This investigation revealed that those with food allergies had a 1.38 times higher rate of cumulative attacks (or relapses) compared with those with no allergies.

While any type of allergy was linked to greater odds of active disease, the food allergy group also showed more than a twofold likelihood of having gadolinium-enhancing lesions on MRI.

Study authors noted that there were not significant differences between the non-allergy group compared with either the environmental or drug allergy groups.

“The fact that other types of allergies did not significantly affect disease activity argues for the role of the gut in MS, though the mechanism is as of yet unclear,” says Asaff Harel, MD, a neurologist at Lenox Hill Hospital in New York City, who was not involved in the investigation.

On the basis of the study results, Chitnis advises people with MS and food allergies to avoid or minimize contact with the foods that they are allergic to, because they could cause more MS disease activity in addition to the allergic symptoms, such as hives, itching, nasal congestion, rashes, watery or red eyes, and tingling or itching in the mouth.

Study Limitations: No Information on MS Medication Type

Dr. Harel points out that the study included a percentage of patients on medication for MS, but did not include information on medication type.

“If the group without allergies happened by chance to be on more efficacious therapies, this could have easily slanted the results,” Harel says.

The research authors stress that the investigation does not demonstrate cause and effect and is limited as an observational study. Also, the questionnaire was issued only once and relied on patient responses, which are subjective.

“Future prospective studies are needed to confirm our findings and understand the underlying biological mechanism, by analyzing blood biomarkers of allergy, which can lead to new therapeutic and preventative strategies for MS,” Chitnis and her coauthors wrote in their conclusion.